[SeongA] WEEK 15 solutions

construct-binary-tree-from-preorder-and-inorder-traversal/delight010.swift

@@ -0,0 +1,26 @@
+class Solution {
+    // Time O(N)
+    // Space O(N)
+    func buildTree(_ preorder: [Int], _ inorder: [Int]) -> TreeNode? {
+        if preorder.isEmpty {
+            return nil
+        }
+
+        let totalCount = preorder.count
+        let rootNode = TreeNode(preorder[0])
+        var rootIndex = 0
+
+        for (index, value) in inorder.enumerated() {
+            if value == rootNode.val {
+                rootIndex = index
+                break
+            }
+        }
+
+        rootNode.left = buildTree(Array(preorder[1..<rootIndex + 1]), Array(inorder[0..<rootIndex + 1]))
+        rootNode.right = buildTree(Array(preorder[1 + rootIndex..<totalCount]), Array(inorder[1 + rootIndex..<totalCount]))
+
+        return rootNode
+    }
+}
+

subtree-of-another-tree/delight010.swift

@@ -0,0 +1,29 @@
+class Solution {
+    // Time O(M * N)
+    // Space O(N)
+    func isSubtree(_ root: TreeNode?, _ subRoot: TreeNode?) -> Bool {
+        if let root = root, let subRoot = subRoot {
+            if root.val == subRoot.val {
+                return dfs(root.left, subRoot: subRoot.left) && dfs(root.right, subRoot: subRoot.right) || isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot)
+            }
+            return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot)
+        }
+
+        return false
+    }
+
+    private func dfs(_ root: TreeNode?, subRoot: TreeNode?) -> Bool {
+        if root == nil && subRoot == nil {
+            return true
+        }
+
+        if let root = root, let subRoot = subRoot {
+            if root.val == subRoot.val {
+                return dfs(root.left, subRoot: subRoot.left) && dfs(root.right, subRoot: subRoot.right)
+            }
+        }
+
+        return false
+    }
+}
+